Conventionally, laminated rotor cores (also referred to as rotor cores) used for motors are manufactured by laminating a plurality of core pieces, inserting permanent magnets into a plurality of magnet insertion holes formed around a central shaft hole, and injecting and curing resin.
This resin injection, for example, as described in Patent Literature 1, is performed by putting a laminated rotor core between an upper die and a lower die of a die after inserting permanent magnets into a plurality of magnet insertion holes, and pushing down plungers from resin reservoir pots provided in the upper die. However, there are problems described below when resin is injected into each magnet insertion hole from above permanent magnets.
Since the height of a laminated rotor core is higher than the heights of permanent magnets, there are slight differences in level (approximately 0.5-1 mm) between the top surface of a laminated rotor core and the top surfaces of permanent magnets. Therefore, resin injected into magnet insertion holes flows in every possible direction through these uneven portions, and since resin is injected into passages (gaps), prioritizing those with large cross-sectional areas, it becomes impossible for the flow of resin to control (fix the permanent magnets on the outer circumferential side by making resin flow into targeted passages, for example, passages on the inner side in the radial direction) the positions of permanent magnets inside each magnet insertion hole. Consequently, positions where permanent magnets are arranged become misaligned (e.g., leaned inward, leaned outward, tilted, etc.) inside each magnet insertion hole, leading to increases in losses, noises and even vibrations when operating a motor.
Also, in Patent Literature 2, a method for manufacturing a laminated rotor core having processes (A)-(K) in FIG. 10 is disclosed. More specifically, the method has the following processes:
(A) Setting up a laminated core body 81 on a carrying tray 80
(B) Tilting the laminated core body 81 together with the carrying tray 80 and inserting permanent magnets 82 into each magnet insertion hole of the laminated core body 81
(C) Setting up a cull plate 83 on the laminated core body 81 after leveling the carrying tray 80
(D) Inverting the carrying tray 80, and the cull plate 83, the carrying tray 80 and the cull plate 83 being in a direct contact with the laminated core body 81
(E) Mounting the laminated core body 81 on a lower die 84, the laminated core body 81 having the carrying tray 80 and the cull plate 83 set up
(F) Holding the laminated core body 81 between an upper die 85 and the lower die 84 and injecting resin into the magnet insertion holes of the laminated core body 81 from the lower die 84, the laminated core body 81 being mounted on the cull plate 83 and further being covered by the carrying tray 80
Additionally, the method has processes (G) and (H) in which the laminated core body 81 is removed from the upper die 85 and the lower die 84, the laminated core body 81 having been resin-sealed and having the cull plate 83 mounted thereunder and the carrying tray 80 mounted thereon. In process (H), there is resin remained in the resin reservoir pots and cured which is adhering to the bottom portion of the cull plate 83. Next, in process (I), the laminated core body 81 is inverted, and after going through process (J) in which the cull plate 83 on the upper portion of the laminated core body 81 is torn off and process (K) in which the resin adhering to the cull plate 83 is removed by using pins 86 in order to reuse the cull plate 83, a resin-sealed laminated rotor core is manufactured. Also, the cull plate 83 has resin passages and gates, the resin passages guiding resin from the resin reservoir pots to magnet insertion holes of a laminated core body 81, the gates being insertion openings for resin flowing into magnet insertion holes.
By injecting resin from the lower die 84 as just described, the bottom surfaces of permanent magnets 82 can be appressed to the cull plate 83. Therefore, when injecting resin, permanent magnets 82 do not lean inward, lean outward or become tilted inside magnet insertion holes, and as compared with a construction method of injecting resin from an upper die, there is an advantage of being able to manufacture a laminated rotor core with alleviated noise and loss, and even with alleviated vibration.